Growth of aromatics and carbonaceous nanoparticles in Claus process

  • Evgenia Georganta

Student thesis: Master's Thesis

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are considered the main precursors for soot formation in the Claus process. Soot particles eventually lead to catalyst deactivation, and thus, have negative impact on plant economics. Careful planning and necessary precautions need to be taken in order to minimize the operational costs and the formation of soot in the Claus process. The aim of this thesis is to study the formation of pyrene, a PAH and a major soot precursor, through the reactions of phenanthrene and methyl radicals under Claus process conditions. The overall reaction is shown below: 2CH 3 -H, -2H2 The methyl radicals are present in the Claus furnace due to the presence of a high amount of methane, which is a contaminant in the acid gas. Although there are experimental evidences that methyl radicals contribute to the formation of PAH, a detailed study to quantify their role in PAH formation and growth is not available in the literature. An improved understanding of the role of methyl radicals in PAH and soot growth may also help in refining the models for natural gas combustion and emissions from them. In this work, the chemically accurate energetics and molecular parameters for the species involved in the reactions in order to form pyrene from phenanthrene were determined through quantum calculations (density functional theory). The rate constants of the elementary reactions have been evaluated using transition state theory. Based on these calculations and potential energy diagrams, the energetically favored pathways for PAH growth by methyl radicals have been suggested. The reaction path analysis was also conducted to determine the most dominant route for pyrene formation in the overall mechanism. Through chemical kinetics simulations of the Claus furnace and the methane flames using a detailed reaction mechanism including the reactions proposed in this work, the contribution of methyl radicals in PAH growth was studied.
Date of Award2016
Original languageAmerican English

Keywords

  • Applied sciences
  • Methyl radicals
  • PAH pyrene
  • Soot
  • Chemical engineering
  • 0542:Chemical engineering

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